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MERSEY UPBEAT

REMEDIATION

Liverpool's new science and technology park will be founded on land which has undergone sophisticated bioremediation to make it suitable for development.

Liverpool is in the ascendancy.

Its status as European City of Culture for 2008 is attracting the investment of hundreds of millions of pounds a year in the city and its environs.

A complex web of development agencies aims to revitalise the region, and sophisticated techniques are helping them take full advantage of land resources.

The city's industrial legacy is gradually being transformed into new employment opportunities.

In Wavertree, one of the gateways to the city centre, the former Mersey Transport tram and bus depot is due to become the Liverpool Science Park. The 6ha site at Edge Lane was a tram depot from 1926 to 1957, when it became a bus depot.

When this closed in 1992, all the buildings were razed to 'oor-slab level and the site was left vacant.

The redevelopment is beginning with reclamation of the site and construction of road, utility and landscape infrastructure. This will support the creation of six plots to provide up to 22,000m2 of commercial space targeted at science and technology industries.

The site, which will include a new public open area, will be linked with the adjacent Liverpool Digital site and the Wavertree Technology Park to create a combined 45ha business park.

The development team is headed by Liverpool Land Development Company, a publicly funded body responsible for the delivery of major physical regeneration projects in four of Liverpool's ' ve strategic investment areas (SIAs).

This first phase of the Liverpool Science Park is funded by English Partnerships. Scott Wilson is the consulting engineer for the project and the main contractor is VHE Construction, the brownfield remediation arm of Montpellier Group, which used its in-house technical arm, VHE Technology.

Scott Wilson's principal project manager Siobhan O'Mahoney says: 'The remediation strategy considered the site's use as a bus and tram depot and results of ground investigations.

'These had identified a number of areas of hydrocarbon contamination, mainly TPH, that potentially required remediation. Also, service records highlighted the presence of an abandoned asbestos cement water main that required removal.' The strategy called for the site to be validated on a 20m by 20m grid basis to identify how much material could be treated for reuse on site.

The overall scope of works included recovery of significant quantities of concrete and minor earthworks as well as the removal of an asbestos water main and the exsitu bio emediation of hydrocarbon contaminated materials.

When VHE Construction began work in December 2004, the first task was breaking out the concrete slab. This was done using a Beaver guillotine to minimise the impact on surrounding properties.

All concrete was processed on site using a combination of screening and crushing techniques to produce 6F2 capping material, Type 1 and drainage stone. Crushed concrete was subjected to chemical analysis on the solid and leachable phase at a rate of one sample per 500m 3. All results were assessed to ensure compliance with remedial targets.

In total site workers removed about 27,000m 3 of concrete which was crushed and replaced on the site as a cover layer and to fill voids created by removal of subsurface obstructions.

VHE Construction proposed processing some of the crushed concrete into valuable Type 1 to full SHW Cl803 speci'cation which will be stockpiled for use in the infrastructure works.

Gordon Wilson, VHE's construction director, says seeing the benefits of recycling materials available on site such as these requires vision beyond the scope of the remediation works.

'This often requires clients to be open-minded about the long term cost benefis, an attitude which in this case the client LLDC was keen to embrace, ' he says.

Testing identified about 1,750m 3 of soil as as failing to meet remedial targets. About 190m 3 of bitumencoated concrete was noncompliant.

VHE Construction and VHE Technology concluded it would not be possible to treat soil economically when hydrocarbon concentrations were greater than 10,000mg/kg.

They also agreed the bitumencoated concrete could not be treated using bioremediation.

A quantity of material with soil concentrations of more than 10,000 mg/kg was identifid and this, along with the bitumen-coated concrete and some asbestos-contaminated material, was removed to the company's own licensed land'll, with the rest deemed suitable for bioremediation.

An ex-situ bioremediation laydown area was built comprising an impermeable membrane with a protective sand layer. Drainage channels were formed on all sides of the laydown area and fed to a temporary above-ground water storage system.

The laydown area was in the centre of the site to ensure it was as far as possible from adjacent properties.

Other control measures for dust, odours and noise were also put in place.

VHE Construction excavated about 400m 3 of material to the bioremediation area where site workers then:

segregated the oversized material for crushing prior to treatment;

formed the materials into treatment windrows on the laydown area;

conditioned the material by integrating additives to promote the bioremediation process;

monitored and sampled the material to prescribe the ongoing treatment required;

aerated and further conditioned the material depending on the level of activity of the bio-remediation process;

confimed compliance with the remediation criteria and hence suitability for reuse in the works.

Bioremediation using windrows began in July. This process was completed by the end of August and the material will be incorporated into the works on final validation this month.

Wilson says: 'There has been a collective commitment to sustainability by English Partnerships as funder, Liverpool Land Development Company as client, Scott Wilson as designer and ourselves as contractor.

'By maximising the use of recycling processes and remediation techniques, the amount of material removed from site has been kept to a minimum, which has reduced the environmental impact.' VHE claims significant cost savings have been made by using bioremediation rather than fullscale offsite disposal to landfill.

The estimated cost of the project is about £1.1M, equating to about £183,000/ha.

Use of bioremediation in the scheme will result in a three- to four-fold reduction of hydrocarbon concentrations in the most contaminated soils treated.

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